Large Area Arrayed Light Valves

ABSTRACT

An additive manufacturing system includes at least two photoconductor plates attached to a substrate. Each photoconductor plate can include separate the Linear Electro layers and transparent conductive oxide layers.

RELATED APPLICATIONS

The present disclosure is a continuation of U.S. patent application Ser.No. 17/513,462, filed Oct. 28, 2021, which claims the benefit of U.S.Patent Application No. 63/107,260, filed Oct. 29, 2020, both of whichare incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure generally relates to large area arrayed lightvalve systems. More particularly, use of arrayed photoconductors fixedto a substrate is described.

BACKGROUND

High power laser systems with light able to operate at high fluence forlong durations are useful for additive manufacturing and otherapplications that can benefit from use of patterned high energy lasers.Unfortunately, light valves used in many conventional high energy/powersystems are limited in size to by how large their photoconductors can begrown. For example, high quality Bismuth Silicate—B₁₂SiO₂₀ (BSO) crystalplates are typically size limited to 30 mm×30 mm since growing largercrystal boules to acquire larger plates results in lower yield due toimpurities and defects. Consequently, light valves resulting from theseplates have a limited clear aperture of ˜30 mm×30 mm. This clearaperture limitation impacts the production rate of a metal additivemanufacturing due to the energy fluence needs to be kept below damagethreshold for a certain area of clear aperture. What is needed aretechniques and structures that can provide large clear apertures bycreating a large area light valve, while still using current costeffective crystal growth methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present disclosureare described with reference to the following figures, wherein likereference numerals refer to like parts throughout the various figuresunless otherwise specified.

FIG. 1A(i-iii) illustrates a photoconductor composite (PC) for enhancedLight Valve (LV) operation

FIG. 1B(i-ii) illustrates an embodiment of a photoconductor compositefor large area LVs;

FIG. 1C illustrates singulation for parallel LV manufacturing;

FIG. 1D illustrates manufacture of arrayed LVs independent of PCthickness;

FIG. 1E illustrates arraying of photoconductor blocks to allow forgeneration of large area photoconductors plates;

FIG. 2 illustrates a block diagram of a high fluence light valve basedadditive manufacturing system supporting a beam dump, a large areaarrayed light valve, and a heat engine;

FIG. 3 illustrates a high fluence large area arrayed light valve basedadditive manufacturing system;

FIG. 4 illustrates another embodiment of a high fluence large areaarrayed light valve based additive manufacturing system; and

FIG. 5 illustrates another embodiment of a high fluence large areaarrayed light valve based additive manufacturing which incorporates aswitchyard approach for recovery and further usage of waste energy.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that form a part thereof, and in which is shown by way ofillustrating specific exemplary embodiments in which the disclosure maybe practiced. These embodiments are described in sufficient detail toenable those skilled in the art to practice the concepts disclosedherein, and it is to be understood that modifications to the variousdisclosed embodiments may be made, and other embodiments may beutilized, without departing from the scope of the present disclosure.The following detailed description is, therefore, not to be taken in alimiting sense.

In the following disclosure, a light valve includes a photoconductorcomposite assembly composed of a photoconductor plate bonded to a stiffand flat supporting substrate.

The photoconductor plate is typically BSO but can be composed of otherphotoconductors.

The supporting substrate material (SSM) is typically C-cut sapphire orcrystalline quartz and can be stiff enough to take on the coating

The bonding material can be sodium silicate.

The SSM can take on many of the anti-reflective (AR) and transparentconductive oxide (TCO) coatings that normally reside on the PC and whichtends to deform the PC. Lack of deformation during the coating processresults easing the LV assembly and optimizing its performance.

Electrical connection can be achieved by creating a supporting substratelarger than the PC and extending the TCO layer beyond the full apertureof the PC such that it is outside high fluence laser (HFL) influence soto optimize available aperture of the PC and maintaining high LV laserdamage threshold.

The PC softness allows it to be deformed and take on the good surfacefigure of the SSM during the compositing process.

In some embodiments a compositing process allows the PC to be polishedwithout resulting in deformation

In some embodiments a compositing process allows the PC externalsurfaces to be coated without resulting in deformation.

In some embodiments a compositing process allows the PC to berefurbished repeatedly.

In some embodiments a compositing process can be applied to an array ofPCs atop a larger supporting substrate to enable a large area LV.

In some embodiments the array is post processed for flatness andcoating.

In some embodiments an array process of composted PCs can be used toallow parallel PC composite manufacturing where PC composite assembliesare singulated from a large area PC composite.

In some embodiments an array process of composited PCs can be used toallow wafer scale manufacturing to be applied to LV construction inwhich the entire LV build process occurs in an automated format.

In one embodiment, the PCs are not polished en masse afterwards toachieve uniform flatness in which case individual secondary substratesare picked & placed and individual LV segments are constructed on thelarge area PC composite.

In some embodiments a process in (a) allows for either a ceramicelectrical connection to be applied or a flex circuit in conjunction tobe applied to reduce the assembly and LV costs.

In some embodiments a flexible LV structures allowed by use of flexibleelectrical backplanes to be used in astronomical or laser weapon system.

In some embodiments a flexible LV structures allow for replacement oftraditional optical systems in which adaption (changing optical responsesuch as zoom lensing or pattern reformatting) is required.

In some embodiments a compositing array method can be applied toconstruction of large area PCs from discrete and high yield blocks ofPCs.

In some embodiments a large area singulated plates can be made byarrayed composite of smaller blocks before final surface finishing andplate singulation.

Large area light valves (LV) can be produced by arranging smalleraffordable and higher yield photoconductor (PC) plates in an array atopa high damage threshold supporting substrate material (SSM) such assapphire. The PC plates can be fixed using atomic or diffusion bonding,etchant-enhanced welding, glass frit epoxy bonding (frit is meant toinclude all forms of glass powder-based epoxies), dissolved glassbonding (also called glass glue) and even certain polymer based epoxybonds.

Lateral arraying can be done with the PC being placed atop sapphireusing glass glue. This arraying can be sometimes called sistering orcompositing of the PC atop the SSM. The arraying can also take placebefore attachment to the SSM by taking bars of the PC harvested from itsboule in a size that guarantees high process yield. The bars areattached using one of the fixation methods to its lateral surfaces andthen sliced into plates as if it originated from a large boule.Sistering/compositing onto the SSM can then occur as if it was a singlehomogeneous plate.

The immediate advantage is the ability to manufacture a LV of large areawithout having to grow a boule to support that size plate. An additionalbenefit of contacting the PC plate to SSM by the same fixation methodallows the PC plate to be made to conform to the flatness of theSSM—which can be controlled to a higher precision than that of the PC(difficult to grow material). The lateral arrayed PC arrangement atopthe SSM can then be processed with enhanced surface figure which mightnot be possible with a single PC plate element without distortion. Suchprocessing can include correcting for PC flatness, wedge and poweraberrations. The ability to control and correct optical aberrations thatare inherent in all LVs while allowing the LV to be arbitrary large is asignificant additional benefit of arraying PCs by this method.

Advantageously, PC flatness enables the Linear Electro layer (LEO,usually liquid crystal) to be well controlled. The LEO layer thicknessuniformity in turn determines the contrast uniformity (in amplitude orphase) across the LV's clear aperture which leads to maximum resolutionand contrast control at the print plane.

Another embodiment provides for a composite of the PC atop the SSM, butwith individual LV cells for each PC placed side by side using discretesecondary substrates. These secondary substrates can provideelectrification to go from the interior to the exterior of the cellwithout compromising PC density/placement using plated through holes oraround edge plating to allow for top side electrification. Since epoxyand conduction lines need to be protected from the high fluence systemtwo ceramic ‘window-frame’ arrays can be placed on either side of the LVwith input side being structured to be non-conductive while the outputside contains protected electrification lines and compliant electricalconnections to ensure electrification the individual LV circuitry.

An additional benefit in compositing individual PC plates to a largerSSM is to allow parallel photoconductor manufacturing by fixingcomponents to a wafer and dicing systems from the wafer only afterpackaging. This method allows for automated processes to be used in LVconstruction, improving yield and reducing cycle and test time.

FIG. 1A(i-iii) illustrate a photoconductor composite (PC) 100A forenhanced Light Valve (LV) operation. Compositing (110A) starts out witha SSM (120A) which contains anti-reflective and transparent conductiveoxide coatings (130A, AR and TCO, respectively) on the interior side.The SSM is one which can be made flat (<λ/10 at 632 nm) across 95% ofits surface and is much stiffer than the PC that is being mated. Thisstiffness can be achieved by using materials naturally strong (i.e.Mohs>9) or by using thicker substrates or a combination of both. The SSMshould have negligible absorption over the wavelength band of expectedoperation. An exemplary transmission band is 990 nm-1070 nm matchingcurrent diode and pulsed laser sources for additive manufacture. The SSMshould also preferably be thermal expansion matched to the PC of choice.The importance of this lies in the many thermal processes requiredduring the manufacturing process including the fixation process itself,polishing processes, coating processes, curing of the alignment layersand LEO layers during LV fabrication, and high power requirements of theLV in operation. Materials that are excellent candidates for thesupporting substrate include C-cut sapphire, 7979 Fused Silica, siliconcarbide, silicon nitride, diamond, calcium fluoride, crystalline quartz,ZnSe, or similar type of materials. A photoconductor (PC) is attached to130A (arrow 150A) between 140A and 130A that can include atomic ordiffusion bonding, etchant-enhanced welding, glass frit epoxy bonding(frit is meant to include all forms of glass powder-based epoxies),dissolved glass bonding (also called glass glue), polymer based epoxybonds or similar fixation methods that would produce a negligibleabsorption, high strength bond, and able to withstand required laserfluences. FIG. 1A(ii) illustrates the resulting structure (160A) thatforms a part of a PC composite assembly. As seen in FIG. 1A(iii) thisassembly (160A) can then be used to construct a LV assembly (170A) thatincludes 160A along with Linear Electro-Optic and spacing assembly(190A) and a secondary substrate which contains a TCO and AR coatinglayer (200A) in a standard LV construction process (220A) to form anassembled composite LV (230A).

There are several benefits that is afforded by using a composite PC. Inmost cases the PC material can include a large number of materialsincluding: Bismuth Silicates (BSO or Bi₁₂SiO₂₀, Bi₆SiO₁₀, Bi₃SiO₅, andsimilar variations), Bismuth Germanate (BGO or Bi₁₂GeO₂₀, Bi₆GeO₁₀,Bi₃GeO₅, and similar variations), Cadmium Selenide (CdSe) and similartype crystals. The photoconductor layer could also be composed ofchalcogenide glasses such as Ge₂Sb₂Te₅ (GST), Sc_(0.2)Sb₂Te₃, GeTe,Ag₄In₃Sb₆₇Te₂₆, Ge₁₅Sb₈₅, or Sb. Additionally, it can be composed ofpolycrystalline materials such as CdTe, AZO, ZnSe, ZnS, or amorphous Si.

A common attribute of these materials is that they are fragile, soft,and lack the stiffness needed for ensuring flat reference surfaces offwhich a LEO layer can be constructed. By sistering or compositing atypical PC (BSO) to a much stiffer substrate, the lack of stiffness oftypical PC becomes an advantage since bonding to the stiffer substratewill make it “follow” the SSM surface figure. Additionally, thesupporting substrate can then be used to allow the exposed PC surface tobe polished flat without risk of the part deforming after fabricationdue to internal stresses.

Typically, the free-standing PC in a LV needs several types of AR andTCO coatings, all of which apply strain to the PC's surfaces resultingin its deformation. It is a common observation that a flat PC prior tocoating becomes dramatically deformed or “potato chipped” after havingthese high strain coatings applied. A flat PC is required to ensure theLEO layer that it is mated to has a uniform thickness since this LVattribute ensures the highest contrast uniformity, best dynamic range,and fastest frame speed of the LV. In this composite case, almost allthe high strain coatings can be applied to the supporting substratebefore compositing the PC to it, eliminating the potential to have awarped PC with the added benefit of now having a stiff PC to which theinterior coating can be applied without risk of PC deformation.

A further advantage of having the supporting substrate having the TCOlayer on it instead of being on the PC is that the supporting substratecan be made larger than the PC extent thus any connection point canreside well outside full aperture of the PC. This enables even greateravailable aperture to be utilized for beam patterning. In existing LVassemblies, care must be taken to ensure the sensitive electricalconnection and glue bonds are protected from flux of the HFL which caninduce laser damage which significantly reduces the available apertureof the device.

An additional advantage of the composting method is the potential forreuse of the PC if it gets damaged during LV operation. It has beenfound that, even with moderate laser damage to the PC, it can berefurbished back to nearly pristine level by a follow-on process whichwill thin the part, but this process poses all of the same risks thatthe initial fabrication process has to a pristine PC plate. Thecomposting method eliminate this risk by enabling refurbishment of thepart supported on the SSM thereby allowing a damaged PC to be returnedto service. If the initial PC was sized to be 1.1 mm thick to start,this refurbishment process allows for >10 refurbishing cycles before thePC is consumed to the point of non-utility.

FIG. 1B(i-ii) illustrates an embodiment of a photoconductor composite(PC) 100B for large area LVs. An array of composited PCs includes anappropriately sized supporting substrate (110B) that affords an areaneeded to accept the number of PCs that will be composited on it, In theexample illustrated with respect to FIG. 1B(i) a 2×2 array or four PCplates (example of one such plate being 130B) are affixed to 110B.Substrate 110B can be coated (120B) prior to pick and placing the PCsand the composite process performed on each/all the PC plates. While thespecification for any one PC plate can be the same (typically 30×30mm×1.1 mm thick), variance on their polishing and processing typicallyresults in plates that are all over their tolerancing limits. The limitswere chosen to afford higher yield (>75% prior to coating). The pick andplace process coupled with the compositing process is illustrated withrespect to FIG. 1B(ii) and results in the side view of the 2×2 exampledepicted in 140B. Instances of PC thickness variation are shown inexaggerated side view. A benefit of the compositing process andstructure is that the supporting substrate can be used as a backingplate and allow the ensemble of PCs placed onto it to be treated as onepart during a polishing process (150B) in which heights variationsacross the collection of PCs in the array are removed and the entirecollection takes on a coplanar surface (depicted in 155B) forming anarray of coplanar composited PCs (160B). The generation of a LV startswith 160B (depicted as 170B) and combined with a LEO assembly (180B,composed of edge epoxy, spacers, and typically includes liquid crystal)and attached to a second supporting substrate (200B) which includes aTCO and AR layer (190B) through a build process, 210B that turns thisinto a large area composited LV (220B).

The benefit of this method is that a light valve can now becomearbitrarily large and is not dependent the PCs growth capability butonly on the capability of making high yield PC plates. All the benefitsmentioned above with a single composited LV can be used in the arrayedversion.

FIG. 1C illustrates singulation for parallel LV manufacturing 100C. Anarrayed PC composition 110C allows for large area pick and place of manyPCs onto a supporting substrate to allow dicing the array up after allthe PCs have been composited to the supporting substrate. An example ofthis is depicted in 120C which shows a large array of composited PCs ona large supporting substrate with three potential areas of interest tobe diced and singulated from this large carrier, a single composted PC(120C), a 2×2 array (140C) and a 3×3 array (150C). These arrays arediced out of 110C and are separately assembled into different sized LVswith 160C, 170C, and 180C associated with 130C, 140C, and 150C,respectively. The benefit of this approach is to allow parallelmanufacturing capabilities to reduce the overall cost of makingcomposited PCs and thus LV. Array polishing as discussed with respect toFIG. 1B(ii) can be performed on the entire array prior to dicing toprovide planar similarity across the entire array and variance reductionfrom panel to panel and on its singulation results.

FIG. 1D illustrates manufacture of arrayed LVs 100D independent of PCthickness. PC plates are picked and placed onto a large area supportsubstrate to form an array of composited PCs (110D). The electricalconnection to the TCO layer is shown as an extension of the TCO into anarea clear of composited PC depicted as 120D. A side view of theresulting LV stack-up (130D) shows that this embodiment contains anon-conductive ceramic protective screen (140D is side view and 200D isplan view), the array of non-planar composite PCs, individual depositedLEO assemblies (160D) on each individual PC interior surface, a AR/TCOlayer (170D) on each of the discrete array of secondary supportsubstrates, a compliant electrical conductive connection attachmentlayer (180D) attached to secondary ceramic protective screen (190D, with200 being the plan view of it). Since each PC plate contains a separateLEO and support substrate, the epoxy defining the spacing and electricalconduction pathways need to be protected from the high fluence lasers(HFL), thus the need for the protective screens (140D and 190D)sandwiching the LV assembly. The second substrate which includes a TCOon the inner side (next to 160D) can have an electrical conduction paththat allows for electrical connectivity external to the LEO layer. Thiscan be done by tailoring the TCO layer on the secondary substrate (220D)with one of several possible methods, two of which are depicted. Theinner surface (the surface in contact with 160D) is coated with anAR/TCO layer, 230D. At one or more corners of 220D (one is depictedhere) is a connection path (240D) from the interior surface to theexterior surface where electrical connection is possible. Edgewrap-deposition (250D) can be used in which a bond line trace extendsfrom a surface to an edge, up the side of the part to an electrical padplaced on the outward side of that part, while the other method is aplated through-hole (260D) in which a hole previously drilled through220D is plated to allow top side electrical connection.

The benefit of this embodiment is not needing the polishing step notedin FIG. 1B(ii) to planarize the PC surfaces with consequent risk ofbreaking, cracking or damaging a composited PC part during the polishingprocess. Additionally, the method allows parallelization of the entireLV assembly using automated manufacturing equipment to drasticallyreduce manufacturing cost of making large area LVs. The topsideelectrification contact points are collected and brought out to an edgecontact point in the 180D layer and is protected from the HFL by 140Dand 190D. Additionally, 180D can be a flex circuit containing a pin gridarray or other compliant electrical connections, easing constructioncomplexity while reducing system costs. An advantage of a flexibleelectrical connection is that singulation of the supporting substratecan be made, after LV array has been assembled, to allow arrayed LVs tobe used for applications that require curvature of the arrays set ofLVs, an example being for adaptive optics on astronomical telescopes orlaser-grade weapon systems, while replacing the primary adaptive opticalsystems. A secondary advantage would be to allow large area LV arrayedassemblies to replace any optical element/system that requires adaptionsuch as zoom lenses or beam reformatting, since LVs can take phaseand/or amplitude response functions.

FIG. 1E illustrates arraying of photoconductor blocks to allow forgeneration of large area photoconductors plates. High yield PC blocks110E and 120E harvested and shaped from the PC boule and composited toeach other through process (depicted by 125E and 130E to form a 1×2 PCblock 140E. This process is repeated 145C and 150E using one or more 1×2blocks to form N×M array of PC block (a 4×2 array is depicted in 150E.150E is processed into plates by 160C by a sawing process and singulatedvia 170E to form a large area PC plate 80E. Advantageously this allowslarge area PC plates to be created without needing to grow largediameter boules.

A wide range of lasers of various wavelengths can used in combinationwith the described phase change light valve system. In some embodiments,possible laser types include, but are not limited to: Gas Lasers,Chemical Lasers, Dye Lasers, Metal Vapor Lasers, Solid State Lasers(e.g. fiber), Semiconductor (e.g. diode) Lasers, Free electron laser,Gas dynamic laser, “Nickel-like” Samarium laser, Raman laser, or Nuclearpumped laser.

A Gas Laser can include lasers such as a Helium-neon laser, Argon laser,Krypton laser, Xenon ion laser, Nitrogen laser, Carbon dioxide laser,Carbon monoxide laser or Excimer laser.

A Chemical laser can include lasers such as a Hydrogen fluoride laser,Deuterium fluoride laser, COIL (Chemical oxygen-iodine laser), or Agil(All gas-phase iodine laser).

A Metal Vapor Laser can include lasers such as a Helium-cadmium (HeCd)metal-vapor laser, Helium-mercury (HeHg) metal-vapor laser,Helium-selenium (HeSe) metal-vapor laser, Helium-silver (HeAg)metal-vapor laser, Strontium Vapor Laser, Neon-copper (NeCu) metal-vaporlaser, Copper vapor laser, Gold vapor laser, or Manganese (Mn/MnCl2)vapor laser. Rubidium or other alkali metal vapor lasers can also beused. A Solid State Laser can include lasers such as a Ruby laser,Nd:YAG laser, NdCrYAG laser, Er:YAG laser, Neodymium YLF (Nd:YLF)solid-state laser, Neodymium doped Yttrium orthovanadate(Nd:YVO4) laser,Neodymium doped yttrium calcium oxoborateNd:YCa4O(BO3)3 or simplyNd:YCOB, Neodymium glass (Nd:Glass) laser, Titanium sapphire(Ti:sapphire) laser, Thulium YAG (Tm:YAG) laser, Ytterbium YAG (Yb:YAG)laser, Ytterbium:2O3 (glass or ceramics) laser, Ytterbium doped glasslaser (rod, plate/chip, and fiber), Holmium YAG (Ho:YAG) laser, ChromiumZnSe (Cr:ZnSe) laser, Cerium doped lithium strontium (orcalcium)aluminum fluoride (Ce:LiSAF, Ce:LiCAF), Promethium 147 dopedphosphate glass (147Pm+3:Glass) solid-state laser, Chromium dopedchrysoberyl (alexandrite) laser, Erbium doped anderbium-ytterbiumco-doped glass lasers, Trivalent uranium doped calcium fluoride (U:CaF2)solid-state laser, Divalent samarium doped calcium fluoride (Sm:CaF2)laser, or F-Center laser.

A Semiconductor Laser can include laser medium types such as GaN, InGaN,AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salt,Vertical cavity surface emitting laser (VCSEL), Quantum cascade laser,Hybrid silicon laser, or combinations thereof.

FIG. 2 illustrates use of a large area light valves such as disclosedherein in an additive manufacturing system 200. A laser source 202directs a laser beam through a laser preamplifier and/or amplifier 204into a large area light valve 206. After patterning, light can bedirected into a print bed 210. In some embodiments, heat or laser energyfrom laser source 202, laser preamplifier and/or amplifier 204, or alarge area light valve 206 can be actively or passively transferred to aheat transfer, heat engine, cooling system, and beam dump 208. Overalloperation of the light valve based additive manufacturing system 200 cancontrolled by one or more controllers 220 that can modify laser powerand timing.

In some embodiments, various preamplifiers or amplifiers 204 areoptionally used to provide high gain to the laser signal, while opticalmodulators and isolators can be distributed throughout the system toreduce or avoid optical damage, improve signal contrast, and preventdamage to lower energy portions of the system 200. Optical modulatorsand isolators can include, but are not limited to Pockels cells, Faradayrotators, Faraday isolators, acousto-optic reflectors, or volume Bragggratings. Pre-amplifier or amplifiers 204 could be diode pumped or flashlamp pumped amplifiers and configured in single and/or multi-pass orcavity type architectures. As will be appreciated, the termpre-amplifier here is used to designate amplifiers which are not limitedthermally (i.e. they are smaller) versus laser amplifiers (larger).Amplifiers will typically be positioned to be the final units in a lasersystem 200 and will be the first modules susceptible to thermal damage,including but not limited to thermal fracture or excessive thermallensing.

Laser pre-amplifiers can include single pass pre-amplifiers usable insystems not overly concerned with energy efficiency. For more energyefficient systems, multi-pass pre-amplifiers can be configured toextract much of the energy from each pre-amplifier 204 before going tothe next stage. The number of pre-amplifiers 204 needed for a particularsystem is defined by system requirements and the stored energy/gainavailable in each amplifier module. Multi-pass pre-amplification can beaccomplished through angular multiplexing or polarization switching(e.g. using waveplates or Faraday rotators).

Alternatively, pre-amplifiers can include cavity structures with aregenerative amplifier type configuration. While such cavity structurescan limit the maximum pulse length due to typical mechanicalconsiderations (length of cavity), in some embodiments “white cell”cavities can be used. A “white cell” is a multi-pass cavity architecturein which a small angular deviation is added to each pass. By providingan entrance and exit pathway, such a cavity can be designed to haveextremely large number of passes between entrance and exit allowing forlarge gain and efficient use of the amplifier. One example of a whitecell would be a confocal cavity with beams injected slightly off axisand mirrors tilted such that the reflections create a ring pattern onthe mirror after many passes. By adjusting the injection and mirrorangles the number of passes can be changed.

Amplifiers are also used to provide enough stored energy to meet systemenergy requirements, while supporting sufficient thermal management toenable operation at system required repetition rate whether they arediode or flashlamp pumped. Both thermal energy and laser energygenerated during operation can be directed the heat transfer, heatengine, cooling system, and beam dump 208.

Amplifiers can be configured in single and/or multi-pass or cavity typearchitectures. Amplifiers can include single pass amplifiers usable insystems not overly concerned with energy efficiency. For more energyefficient systems, multi-pass amplifiers can be configured to extractmuch of the energy from each amplifier before going to the next stage.The number of amplifiers needed for a particular system is defined bysystem requirements and the stored energy/gain available in eachamplifier module. Multipass pre-amplification can be accomplishedthrough angular multiplexing, polarization switching (waveplates,Faraday rotators). Alternatively, amplifiers can include cavitystructures with a regenerative amplifier type configuration. Asdiscussed with respect to pre-amplifiers, amplifiers can be used forpower amplification.

In some embodiments, thermal energy and laser energy generated duringoperation of system 200 can be directed into the heat transfer, heatengine, cooling system, and beam dump 208. Alternatively, or inaddition, in some embodiments the beam dump 208 can be a part of a heattransfer system to provide useful heat to other industrial processes. Instill other embodiments, the heat can be used to power a heat enginesuitable for generating mechanical, thermoelectric, or electric power.In some embodiments, waste heat can be used to increase temperature ofconnected components. As will be appreciated, laser flux and energy canbe scaled in this architecture by adding more pre-amplifiers andamplifiers with appropriate thermal management and optical isolation.Adjustments to heat removal characteristics of the cooling system arepossible, with increase in pump rate or changing cooling efficiencybeing used to adjust performance.

FIG. 3 illustrates an additive manufacturing system 300 that canaccommodate large area light valves as described in this disclosure. Asseen in FIG. 3 , a laser source and amplifier(s) 312 can include largearea light valves and laser amplifiers and other components such aspreviously described. As illustrated in FIG. 3 , the additivemanufacturing system 300 uses lasers able to provide one or twodimensional directed energy as part of a laser patterning system 310. Insome embodiments, one dimensional patterning can be directed as linearor curved strips, as rastered lines, as spiral lines, or in any othersuitable form. Two-dimensional patterning can include separated oroverlapping tiles, or images with variations in laser intensity.Two-dimensional image patterns having non-square boundaries can be used,overlapping or interpenetrating images can be used, and images can beprovided by two or more energy patterning systems. The laser patterningsystem 310 uses laser source and amplifier(s) 312 to direct one or morecontinuous or intermittent energy beam(s) toward beam shaping optics314. After shaping, if necessary, the beam is patterned by a laserpatterning unit 316 that includes either a transmissive or reflectivelight valve, with generally some energy being directed to a rejectedenergy handling unit 318. The rejected energy handling unit can utilizeheat provided by active of cooling of light.

Patterned energy is relayed by image relay 320 toward an articleprocessing unit 340, in one embodiment as a two-dimensional image 322focused near a bed 346. The bed 346 (with optional walls 348) can form achamber containing material 344 (e.g. a metal powder) dispensed bymaterial dispenser 342. Patterned energy, directed by the image relay320, can melt, fuse, sinter, amalgamate, change crystal structure,influence stress patterns, or otherwise chemically or physically modifythe dispensed material 344 to form structures with desired properties. Acontrol processor 350 can be connected to variety of sensors, actuators,heating or cooling systems, monitors, and controllers to coordinateoperation of the laser source and amplifier(s) 312, beam shaping optics314, laser patterning unit 316, and image relay 320, as well as anyother component of system 300. As will be appreciated, connections canbe wired or wireless, continuous or intermittent, and include capabilityfor feedback (for example, thermal heating can be adjusted in responseto sensed temperature).

In some embodiments, beam shaping optics 314 can include a great varietyof imaging optics to combine, focus, diverge, reflect, refract,homogenize, adjust intensity, adjust frequency, or otherwise shape anddirect one or more laser beams received from the laser source andamplifier(s) 312 toward the laser patterning unit 316. In oneembodiment, multiple light beams, each having a distinct lightwavelength, can be combined using wavelength selective mirrors (e.g.dichroics) or diffractive elements. In other embodiments, multiple beamscan be homogenized or combined using multifaceted mirrors, microlenses,and refractive or diffractive optical elements.

Laser patterning unit 316 can include static or dynamic energypatterning elements. For example, laser beams can be blocked by maskswith fixed or movable elements. To increase flexibility and ease ofimage patterning, pixel addressable masking, image generation, ortransmission can be used. In some embodiments, the laser patterning unitincludes addressable light valves, alone or in conjunction with otherpatterning mechanisms to provide patterning. The light valves can betransmissive, reflective, or use a combination of transmissive andreflective elements. Patterns can be dynamically modified usingelectrical or optical addressing. In one embodiment, a transmissiveoptically addressed light valve acts to rotate polarization of lightpassing through the valve, with optically addressed pixels formingpatterns defined by a light projection source. In another embodiment, areflective optically addressed light valve includes a write beam formodifying polarization of a read beam. In certain embodiments,non-optically addressed light valves can be used. These can include butare not limited to electrically addressable pixel elements, movablemirror or micro-mirror systems, piezo or micro-actuated optical systems,fixed or movable masks, or shields, or any other conventional systemable to provide high intensity light patterning.

Rejected energy handling unit 318 is used to disperse, redirect, orutilize energy not patterned and passed through the image relay 320. Inone embodiment, the rejected energy handling unit 318 can includepassive or active cooling elements that remove heat from both the lasersource, light valve(s), and amplifier(s) 312 and the laser patterningunit 316. In other embodiments, the rejected energy handling unit caninclude a “beam dump” to absorb and convert to heat any beam energy notused in defining the laser pattern. In still other embodiments, rejectedlaser beam energy can be recycled using beam shaping optics 314.Alternatively, or in addition, rejected beam energy can be directed tothe article processing unit 340 for heating or further patterning. Incertain embodiments, rejected beam energy can be directed to additionalenergy patterning systems or article processing units.

In one embodiment, a “switchyard” style optical system can be used.Switchyard systems are suitable for reducing the light wasted in theadditive manufacturing system as caused by rejection of unwanted lightdue to the pattern to be printed. A switchyard involves redirections ofa complex pattern from its generation (in this case, a plane whereupon aspatial pattern is imparted to structured or unstructured beam) to itsdelivery through a series of switch points. Each switch point canoptionally modify the spatial profile of the incident beam. Theswitchyard optical system may be utilized in, for example and notlimited to, laser-based additive manufacturing techniques where a maskis applied to the light. Advantageously, in various embodiments inaccordance with the present disclosure, the thrown-away energy may berecycled in either a homogenized form or as a patterned light that isused to maintain high power efficiency or high throughput rates.Moreover, the thrown-away energy can be recycled and reused to increaseintensity to print more difficult materials.

Image relay 320 can receive a patterned image (either one ortwo-dimensional) from the laser patterning unit 316 directly or througha switchyard and guide it toward the article processing unit 340. In amanner similar to beam shaping optics 314, the image relay 320 caninclude optics to combine, focus, diverge, reflect, refract, adjustintensity, adjust frequency, or otherwise shape and direct the patternedlight. Patterned light can be directed using movable mirrors, prisms,diffractive optical elements, or solid state optical systems that do notrequire substantial physical movement. One of a plurality of lensassemblies can be configured to provide the incident light having themagnification ratio, with the lens assemblies both a first set ofoptical lenses and a second sets of optical lenses, and with the secondsets of optical lenses being swappable from the lens assemblies.Rotations of one or more sets of mirrors mounted on compensatinggantries and a final mirror mounted on a build platform gantry can beused to direct the incident light from a precursor mirror onto a desiredlocation. Translational movements of compensating gantries and the buildplatform gantry are also able to ensure that distance of the incidentlight from the precursor mirror the article processing unit 340 issubstantially equivalent to the image distance. In effect, this enablesa quick change in the optical beam delivery size and intensity acrosslocations of a build area for different materials while ensuring highavailability of the system.

Article processing unit 340 can include a walled chamber 348 and bed 344(collectively defining a build chamber), and a material dispenser 342for distributing material. The material dispenser 342 can distribute,remove, mix, provide gradations or changes in material type or particlesize, or adjust layer thickness of material. The material can includemetal, ceramic, glass, polymeric powders, other melt-able materialcapable of undergoing a thermally induced phase change from solid toliquid and back again, or combinations thereof. The material can furtherinclude composites of melt-able material and non-melt-able materialwhere either or both components can be selectively targeted by theimaging relay system to melt the component that is melt-able, whileeither leaving along the non-melt-able material or causing it to undergoa vaporizing/destroying/combusting or otherwise destructive process. Incertain embodiments, slurries, sprays, coatings, wires, strips, orsheets of materials can be used. Unwanted material can be removed fordisposable or recycling by use of blowers, vacuum systems, sweeping,vibrating, shaking, tipping, or inversion of the bed 346.

In addition to material handling components, the article processing unit340 can include components for holding and supporting 3D structures,mechanisms for heating or cooling the chamber, auxiliary or supportingoptics, and sensors and control mechanisms for monitoring or adjustingmaterial or environmental conditions. The article processing unit can,in whole or in part, support a vacuum or inert gas atmosphere to reduceunwanted chemical interactions as well as to mitigate the risks of fireor explosion (especially with reactive metals). In some embodiments,various pure or mixtures of other atmospheres can be used, includingthose containing Ar, He, Ne, Kr, Xe, CO₂, N₂, O₂, SF₆, CH₄, CO, N₂O,C₂H₂, C₂H₄, C₂H₆, C₃H₆, C₃H₈, i-C₄H₁₀, C₄H₁₀, 1-C₄H₈, cic-2,C₄H₇,1,3-C₄H₆, 1,2-C4H6, C₅H₁₂, n-C₅H₁₂, i-C₅H₁₂, n-C6H₁₄, C₂H₃Cl, C₇H₁₆,C₈H₁₈, C₁₀H₂₂, C₁₁H₂₄, C₁₂H₂₆, C₁₃H₂₈, C₁₄H₃₀, C₁₅H₃₂, C₁₆H₃₄, C₆H₆,C₆H₅—CH₃, C₈H₁₀, C₂H₅OH, CH₃OH, iC₄H₈. In some embodiments, refrigerantsor large inert molecules (including but not limited to sulfurhexafluoride) can be used. An enclosure atmospheric composition to haveat least about 1% He by volume (or number density), along with selectedpercentages of inert/non-reactive gasses can be used.

In certain embodiments, a plurality of article processing units or buildchambers, each having a build platform to hold a powder bed, can be usedin conjunction with multiple optical-mechanical assemblies arranged toreceive and direct the one or more incident energy beams into the buildchambers. Multiple chambers allow for concurrent printing of one or moreprint jobs inside one or more build chambers. In other embodiments, aremovable chamber sidewall can simplify removal of printed objects frombuild chambers, allowing quick exchanges of powdered materials. Thechamber can also be equipped with an adjustable process temperaturecontrols. In still other embodiments, a build chamber can be configuredas a removable printer cartridge positionable near laser optics. In someembodiments a removable printer cartridge can include powder or supportdetachable connections to a powder supply. After manufacture of an item,a removable printer cartridge can be removed and replaced with a freshprinter cartridge.

In another embodiment, one or more article processing units or buildchambers can have a build chamber that is maintained at a fixed height,while optics are vertically movable. A distance between final optics ofa lens assembly and a top surface of powder bed a may be managed to beessentially constant by indexing final optics upwards, by a distanceequivalent to a thickness of a powder layer, while keeping the buildplatform at a fixed height. Advantageously, as compared to a verticallymoving the build platform, large and heavy objects can be more easilymanufactured, since precise micron scale movements of the ever changingmass of the build platform are not needed. Typically, build chambersintended for metal powders with a volume more than ˜0.1-0.2 cubic meters(i.e., greater than 100-200 liters or heavier than 500-1,000 kg) willmost benefit from keeping the build platform at a fixed height.

In one embodiment, a portion of the layer of the powder bed may beselectively melted or fused to form one or more temporary walls out ofthe fused portion of the layer of the powder bed to contain anotherportion of the layer of the powder bed on the build platform. Inselected embodiments, a fluid passageway can be formed in the one ormore first walls to enable improved thermal management.

In some embodiments, the additive manufacturing system can includearticle processing units or build chambers with a build platform thatsupports a powder bed capable of tilting, inverting, and shaking toseparate the powder bed substantially from the build platform in ahopper. The powdered material forming the powder bed may be collected ina hopper for reuse in later print jobs. The powder collecting processmay be automated and vacuuming or gas jet systems also used to aidpowder dislodgement and removal.

Some embodiments, the additive manufacturing system can be configured toeasily handle parts longer than an available build chamber. A continuous(long) part can be sequentially advanced in a longitudinal directionfrom a first zone to a second zone. In the first zone, selected granulesof a granular material can be amalgamated. In the second zone,unamalgamated granules of the granular material can be removed. Thefirst portion of the continuous part can be advanced from the secondzone to a third zone, while a last portion of the continuous part isformed within the first zone and the first portion is maintained in thesame position in the lateral and transverse directions that the firstportion occupied within the first zone and the second zone. In effect,additive manufacture and clean-up (e.g., separation and/or reclamationof unused or unamalgamated granular material) may be performed inparallel (i.e., at the same time) at different locations or zones on apart conveyor, with no need to stop for removal of granular materialand/or parts.

In another embodiment, additive manufacturing capability can be improvedby use of an enclosure restricting an exchange of gaseous matter betweenan interior of the enclosure and an exterior of the enclosure. Anairlock provides an interface between the interior and the exterior;with the interior having multiple additive manufacturing chambers,including those supporting power bed fusion. A gas management systemmaintains gaseous oxygen within the interior at or below a limitingoxygen concentration, increasing flexibility in types of powder andprocessing that can be used in the system.

In another manufacturing embodiment, capability can be improved byhaving an article processing units or build chamber contained within anenclosure, the build chamber being able to create a part having a weightgreater than or equal to 2,000 kilograms. A gas management system maymaintain gaseous oxygen within the enclosure at concentrations below theatmospheric level. In some embodiments, a wheeled vehicle may transportthe part from inside the enclosure, through an airlock, since theairlock operates to buffer between a gaseous environment within theenclosure and a gaseous environment outside the enclosure, and to alocation exterior to both the enclosure and the airlock.

Other manufacturing embodiments involve collecting powder samples inreal-time from the powder bed. An ingester system is used for in-processcollection and characterizations of powder samples. The collection maybe performed periodically and the results of characterizations result inadjustments to the powder bed fusion process. The ingester system canoptionally be used for one or more of audit, process adjustments oractions such as modifying printer parameters or verifying proper use oflicensed powder materials.

Yet another improvement to an additive manufacturing process can beprovided by use of a manipulator device such as a crane, lifting gantry,robot arm, or similar that allows for the manipulation of parts thatwould be difficult or impossible for a human to move is described. Themanipulator device can grasp various permanent or temporary additivelymanufactured manipulation points on a part to enable repositioning ormaneuvering of the part.

Control processor 350 can be connected to control any components ofadditive manufacturing system 300 described herein, including lasers,laser amplifiers, optics, heat control, build chambers, and manipulatordevices. The control processor 350 can be connected to variety ofsensors, actuators, heating or cooling systems, monitors, andcontrollers to coordinate operation. A wide range of sensors, includingimagers, light intensity monitors, thermal, pressure, or gas sensors canbe used to provide information used in control or monitoring. Thecontrol processor can be a single central controller, or alternatively,can include one or more independent control systems. The controllerprocessor 350 is provided with an interface to allow input ofmanufacturing instructions. Use of a wide range of sensors allowsvarious feedback control mechanisms that improve quality, manufacturingthroughput, and energy efficiency.

One embodiment of operation of a manufacturing system supporting use ofa large area light valve suitable for additive or subtractivemanufacture is illustrated in FIG. 4 . In this embodiment, a flow chart400 illustrates one embodiment of a manufacturing process supported bythe described optical and mechanical components. In step 402, materialis positioned in a bed, chamber, or other suitable support. The materialcan be a metal plate for laser cutting using subtractive manufacturetechniques, or a powder capable of being melted, fused, sintered,induced to change crystal structure, have stress patterns influenced, orotherwise chemically or physically modified by additive manufacturingtechniques to form structures with desired properties.

In step 404, unpatterned laser energy is emitted by one or more energyemitters, including but not limited to solid state or semiconductorlasers, and then amplified by one or more laser amplifiers. In step 406,the unpatterned laser energy is shaped and modified (e.g. intensitymodulated or focused). In step 408, this unpatterned laser energy ispatterned by a large area light valve, with energy not forming a part ofthe pattern being handled in step 410 (this can include use of a beamdump as disclosed with respect to FIG. 2 and FIG. 3 that provideconversion to waste heat, recycling as patterned or unpatterned energy,or waste heat generated by cooling the laser amplifiers in step 404). Instep 412, the patterned energy, now forming a one or two-dimensionalimage is relayed toward the material. In step 414, the image is appliedto the material, either subtractively processing or additively buildinga portion of a 3D structure. For additive manufacturing, these steps canbe repeated (loop 416) until the image (or different and subsequentimage) has been applied to all necessary regions of a top layer of thematerial. When application of energy to the top layer of the material isfinished, a new layer can be applied (loop 418) to continue building the3D structure. These process loops are continued until the 3D structureis complete, when remaining excess material can be removed or recycled.

FIG. 5 is one embodiment of an additive manufacturing system thatincludes a large area light valve and a switchyard system enabling reuseof patterned two-dimensional energy. An additive manufacturing system520 has an energy patterning system with a laser and amplifier source512 that directs one or more continuous or intermittent laser beam(s)toward beam shaping optics 514. Excess heat can be transferred into arejected energy handling unit 522 that can include an active light valvecooling system as disclosed with respect FIG. 2 , FIG. 3 , and FIG. 4 .After shaping, the beam is two-dimensionally patterned by an energypatterning unit 530, with generally some energy being directed to therejected energy handling unit 522. Patterned energy is relayed by one ofmultiple image relays 532 toward one or more article processing units534A, 534B, 534C, or 534D, typically as a two-dimensional image focusednear a movable or fixed height bed. The bed can be inside a cartridgethat includes a powder hopper or similar material dispenser. Patternedlaser beams, directed by the image relays 532, can melt, fuse, sinter,amalgamate, change crystal structure, influence stress patterns, orotherwise chemically or physically modify the dispensed material to formstructures with desired properties.

In this embodiment, the rejected energy handling unit has multiplecomponents to permit reuse of rejected patterned energy. Coolant fluidfrom the laser amplifier and source 512 can be directed into one or moreof an electricity generator 524, a heat/cool thermal management system525, or an energy dump 526. Additionally, relays 528A, 528B, and 528Ccan respectively transfer energy to the electricity generator 524, theheat/cool thermal management system 525, or the energy dump 526.Optionally, relay 528C can direct patterned energy into the image relay532 for further processing. In other embodiments, patterned energy canbe directed by relay 528C, to relay 528B and 528A for insertion into thelaser beam(s) provided by laser and amplifier source 512. Reuse ofpatterned images is also possible using image relay 532. Images can beredirected, inverted, mirrored, sub-patterned, or otherwise transformedfor distribution to one or more article processing units. 534A-D.Advantageously, reuse of the patterned light can improve energyefficiency of the additive manufacturing process, and in some casesimprove energy intensity directed at a bed or reduce manufacture time.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims. It is also understood that other embodiments of this inventionmay be practiced in the absence of an element/step not specificallydisclosed herein.

1. A light valve, comprising: a substrate; and at least twophotoconductor plates attached to the substrate.
 2. The light valve ofclaim 1, wherein the substrate is sapphire.
 3. The light valve of claim1, wherein the at least two photoconductor plates attached to thesubstrate are laterally positioned with respect to each other.
 4. Thelight valve of claim 1, wherein the at least two photoconductor platesare attached to the substrate with a glass glue.
 5. The light valve ofclaim 1, wherein the at least two photoconductor plates are thermalexpansion matched to the substrate.
 6. The light valve of claim 1,wherein the at least two photoconductor plates are each attached tosecondary substrates that are each attached to the substrate.
 7. Thelight valve of claim 1, wherein the at least two photoconductor platesinclude at least one of Bismuth Silicates, Bismuth Germanates, CadmiumSelenides, chalcogenide glasses, polycrystalline materials, or amorphoussilicon.
 8. The light valve of claim 1, wherein the at least twophotoconductor plates include at least one of BSO, Bi₁₂SiO₂₀, Bi₆SiO₁₀,Bi₃SiO₅, Bismuth Germanates, BGO, Bi₁₂GeO₂₀, Bi₆GeO₁₀, Bi₃GeO₅, CdSe,Ge₂Sb₂Te₅ (GST), Sc_(0.2)Sb₂Te₃, GeTe, Ag₄In₃Sb₆₇Te₂₆, Ge₁₅Sb₈₅, Sb,CdTe, AZO, ZnSe, ZnS, or Si.
 9. The light valve of claim 1, wherein theat least two photoconductor plates form a N×M array on the substrate.10. The light valve of claim 1, wherein the at least two photoconductorplates each has a linear electro (LEO) layer and a transparentconductive oxide (TCO) layer.
 11. An additive manufacturing system,comprising a laser light source to form a laser beam; a light valvesupporting two-dimensional patterning of the light beam, the light valveincluding a substrate; and at least two photoconductor plates attachedto the substrate.
 12. The additive manufacturing system of claim 11,wherein the substrate is sapphire.
 13. The additive manufacturing systemof claim 11, wherein the at least two photoconductor plates attached tothe substrate are laterally positioned with respect to each other. 14.The additive manufacturing system of claim 11, wherein the at least twophotoconductor plates are attached to the substrate with a glass glue.15. The additive manufacturing system of claim 11, wherein the at leasttwo photoconductor plates are thermal expansion matched to thesubstrate.
 16. The additive manufacturing system of claim 11, whereinthe at least two photoconductor plates are each attached to secondarysubstrates that are each attached to the substrate.
 17. The additivemanufacturing system of claim 11, wherein the at least twophotoconductor plates include at least one of Bismuth Silicates, BismuthGermanates, Cadmium Selenides, chalcogenide glasses, polycrystallinematerials, or amorphous silicon.
 18. The additive manufacturing systemof claim 11, wherein the at least two photoconductor plates include atleast one of BSO, Bi₁₂SiO₂₀, Bi₆SiO₁₀, Bi₃SiO₅, Bismuth Germanates, BGO,Bi₁₂GeO₂₀, Bi₆GeO₁₀, Bi₃GeO₅, CdSe, Ge₂Sb₂Te₅ (GST), Sc_(0.2)Sb₂Te₃,GeTe, Ag₄In₃Sb₆₇Te₂₆, Ge₁₅Sb₈₅, Sb, CdTe, AZO, ZnSe, ZnS, or Si.
 19. Theadditive manufacturing system of claim 11, wherein the at least twophotoconductor plates form a N×M array on the substrate.
 20. Theadditive manufacturing system of claim 11, wherein the at least twophotoconductor plates each has a linear electro (LEO) layer and atransparent conductive oxide (TCO) layer.